Resilient retaining rings such as "snap rings," are employed to maintain the position of elements on shafts and within bores. To facilitate removal and installation, rings are formed with apertures near their ends by which such a ring is engaged by a suitable tool and then either expanded or contracted.
Retaining rings used to retain elements such as bearings, gears or pulleys on shafts are known as "external" rings. An external ring normally engages an annular groove formed in a shaft to inhibit axial movement of a shaft mounted element. The external-type ring is installed by expanding the ring until its diameter is greater than the shaft diameter.
A retaining ring used to retain an element such as a bearing or shaft within a bore is known as an "internal" ring. In order to install an internal-type ring it is contracted in order to pass into the bore and then allowed to expand into an internal groove formed around the bore.
Hand tools for installing and removing retaining rings are available, as for example those described in J. Edward C. Anderson's U.S. Pat. Nos. 4,621,401 and 4,625,379. Most known hand tools are not suitable for manipulating very large snap rings which may be of the order of a foot in diameter and even larger. One tool used for manipulating such large rings comprises two crossed arms pivotally connected together, one of which includes a ratchet wheel. The operator forces the retaining ring open or closed by opening or closing the arms stepwise while the ratchet prevents the elastic forces from restoring the ring to its original shape.
One difficulty with this approach is that the handles must be very long in order to provide sufficient mechanical advantage for the operator to manually deform the ring. Since the tool is so long, it is clumsy to manipulate, particular in narrow places. Furthermore, the tool requires great operator strength and stamina.
As an alternative an hydraulic tool has been proposed as disclosed in U.S. Pat. No. 4,351,097 to Hashimoto et al. The proposed tool is likewise difficult to use since an operator must manually pump fluid from an internal hydraulic fluid reservoir. The pump and reservoir increase the weight and complexity of the tool. Further, the Hashimoto proposal requires different and interchangeable complex cam actuated mechanisms for internal and external rings.